Security has been beefed up in UK cities and ports in the wake of the Paris attacks, with Britons being urged to remain vigilant.
Speaking after a meeting of UK government’s Cobra emergency committee, Home Secretary Theresa May said the UK authorities were working to help find anyone involved in the “barbaric attacks” in the French capital, and confirmed British police and spies were assisting the international manhunt.
It came as Prime Minister David Cameron said the UK’s safety and security depended on “degrading and ultimately destroying” the Islamic State (IS) “death cult”.
The Home Secretary said extra security measures had been put in place around Britain and that “people will see increased security at the borders, increased checks taking place”.
“There is also some increased police presence in major cities as well,” she said, although the terror threat level has not been changed from its existing, second-highest “severe” rating.
Ms May said there were “tried and tested” measures for the military to respond to a marauding attack by terrorist gunmen.
A “handful” of Britons are feared to have died in the attacks.
Nick Alexander, 36, from Colchester, the only confirmed British fatality, had been selling merchandise for rock group Eagles of Death Metal when their concert at the Bataclan venue was targeted.
A team from the Foreign Office has travelled to Paris to assist Britons injured or traumatised by the violence.
The British ambassador to France, Sir Peter Ricketts, said it was hard to be exact about the number of injured Britons as people were in various hospitals across Paris.
Reports have suggested UK special forces are geared to intervene if an attack similar to the one carried out in Paris is attempted on British soil.
Setting out the British response, the Home Secretary said: “The UK police and security services are working very closely with their counterparts in France and Belgium to identify all those involved and to pursue anyone who may have been involved in the preparation of these barbaric attacks.”
She added: “The UK stands shoulder to shoulder in solidarity with France. The terrorists will not win, we will defeat them.”
Meanwhile, a one-minute silence will be held in the UK at 11am today, part of a Europe-wide silence at midday French time.
In an update following the Cobra meeting, Downing Street said “we encourage people to join in” the minute’s silence “as a signal of solidarity”.
Mr Cameron is at the G20 summit in Turkey, where he will today urge Russian president Vladimir Putin to focus his country’s firepower on destroying IS.
He will voice the West’s concern that Russian air strikes are targeting moderate opponents of Syrian president Bashar al-Assad rather than the terror group that has claimed responsibility for the slaughter on the streets of Paris.
Speaking shortly after leaders of the world’s major economies bowed their heads for a minute’s silence in honour of victims of terror in Paris and the Turkish capital Ankara, Mr Cameron said that Britain and the rest of the world would be safer if IS was destroyed “once and for all”.
The Prime Minister said that the murders in Paris had made it even clearer that the fight against the terror group must take place both in Iraq and Syria.
He has long argued that RAF missions against IS in Iraq should be extended to Syria, where the US and France are already conducting air strikes.
Mr Cameron said: “The conversation I want to have with Vladimir Putin is to say, ‘Look, there is one thing we agree about which is we’d be safer in Russia, we’d be safer in Britain if we destroy Isil [IS].”